Table II.
Kinetic constants of mutated CH3 and SHT proteins with tyramine and serotonin as amine substrates
Feruloyl-CoA (250 μm) was used as the acyl donor. ND, Not detected.
| Enzyme
|
Tyramine
|
Serotonin
|
||||
|---|---|---|---|---|---|---|
| Km | Vmax | Vmax/Km | Km | Vmax | Vmax/Km | |
| μm | nkat mg−1 | μm | nkat mg−1 | |||
| CH3 | 16,658 | 9.4 | 0.0005 | 2,360 | 27.0 | 0.0114 |
| CH3-S153N | 28,000 | 19.1 | 0.0007 | 3,789 | 19.1 | 0.0050 |
| CH3-L156C | 27,900 | 30.1 | 0.0011 | 2,382 | 16.3 | 0.0068 |
| CH3-G158Y | 25,800 | 32.2 | 0.0012 | 7,006 | 14.8 | 0.0021 |
| THT | 40 | 66.8 | 1.6750 | ND | ND | ND |
| THT-SLG | 17,000 | 9.0 | 0.0005 | ND | ND | ND |
| SHT | 1,165 | 17.0 | 0.0146 | 73 | 6.5 | 0.0890 |
| SHT-S153N | 1,325 | 55.3 | 0.0417 | 129 | 9.1 | 0.0705 |
| SHT-L156C | 1,739 | 40.8 | 0.0234 | 44 | 6.6 | 0.1500 |
| SHT-G158Y | 14,951 | 5.1 | 0.0003 | 19,876 | 29.4 | 0.0015 |
| SHT-NCY | 31,541 | 7.2 | 0.0002 | 7,546 | 15.7 | 0.0020 |
| SHT-Y149F | 160 | 15.5 | 0.0968 | 1,513 | 7.5 | 0.0049 |
| SHT-F151Y | 783 | 7.6 | 0.0097 | 450 | 5.8 | 0.0128 |
| SHT-FY | 1,370 | 5.8 | 0.0042 | 4,051 | 4.0 | 0.0010 |